FIG. 1 shows an example of an electric machine. This particular machine is an electrical motor/generator with permanent magnets. Redundancy in aircraft and other environments is used to increase safety and reliability. In aircraft electrical systems associated with aircraft engines sometimes electric machines are provided with multi-machine redundancies—i.e. two or more machines provided, instead of just one. Alternately, electric machines like the one illustrated in FIG. 1, or other type described in applicants U.S. Pat. No. 6,965,183, for instance, can be designed with two or more substantially independent channels or stator sections, and thus provide an intrinsically redundant design. An advantage of having more than one machine, or more than one channel in a machine, is that in the event of a fault in one machine or channel which requires it to be shutdown the remaining machine(s) or channel(s) can continue to operate.
Various monitoring systems and methods are used for detecting faults in electric machines while they operate. Although these various systems and methods have been satisfactory to a certain degree, there is still a need to provide new and better ways of detecting and possibly preventing faults in electric machines.